The invention relates to an outer wall with plate-like sound dampening elements which are suspended on a metal structure with cross bars made of structural steel.
Such cross bar structures for supporting an outer wall constructed by dampening elements having a rear vented facade liner are particularly used in the construction of power plants for cost and weight saving reasons. Thereby, a sound emission diagram is first defined which shows the sound stress in the various frequencies caused by the machines, devices and installations in the enclosed space. Since a defined sound emission cannot be exceeded on the property borders, it is necessary to provide a defined sound dampening in the corresponding frequencies, due to the sound stress. This sound dampening is obtained by dampening elements which are mounted on the outer side of the cross bars and which in a free suspension bridge the intermediary space between the cross bars and consist, for example, of mineral fiber dampening material elements with an edge side metal flashing which are covered on both sides by asbestos cement or asbestos silicon plates. The cover plates may have different thicknesses and form a particularly effective sound dampening element together with the hollow space dampening from the mineral fiber dampening material plate, depending on the coordination in the desired frequencies. The sound dampening effect substantially depends from the density of the sound dampening elements, so that the same are comparably heavy. The facade lining, for example, made of aluminum trapeze sheet metal, asbestos cement corrugated plates, or the like, serve as a weather protection for the free side of the sound dampening elements.
Weld bolts are used for mounting the sound dampening elements and the facade liner on the cross bars. Weld bolts made of structural steel with a sufficient hardness are used to assure a safe weld connection which can support the weight of the heat dampening elements which are mounted on the thread weld bolt and the weight of the facade liner; for example, the cross bars and the weld bolts may consist of steel St 37 in accordance with the German Industrial Standard DIN 17 100, wherein the weld bolts are provided with a specific material design at the end to be welded, in a known manner, so as to affect the welding process during the passing of current. The setting of the weld bolts must be carried out with great precision, whereby a sink hole is provided at the location where the given weld bolt is engaged, for a local removal of the rust protection paint of the cross bar and for exposing the blank metal for engaging the given weld bolt, whereby the end of the weld bolt is inserted into the sink bore and welded therewith by means of a welding machine. After welding, a rust protection painting is performed in the welding area and the thread welding bolt.
After setting of the thread weld bolts in the aforementioned manner, the sound dampening elements are mounted on the rows of weld bolts in the known outer wall and are pushed thereupon by means of nuts which are screwed onto the thread weld bolt ends with intermediary mounted distance clamping profiles. Thereby, the thread ends of the thread weld bolts protrude by such a length beyond the clamping nuts, thus enabling the facade lining to be fastened by a support nut on its outside, after being installed.
From the assembly point of view, it is disadvantageous that the clamping nut for fixing the sound dampening element must be screwed through the total long segment of the thread welding bolts which extends beyond the sound dampening element, thus requiring a substantial additional amount of time in view of the large number of thread weld bolts of a facade or ceiling wall. The rust protection paint of the "cold" area outside of the sound dampening elements, which also result in a certain heat dampening, the thread bolt is already exposed to damages over a long thread segment by screwing on the clamping nut, so that corrosion can occur, if the paint is not immediately replaced, which again requires a considerable amount of time. Despite of such an after repair, the rust protection paint remains in danger due to mechanical effects, thus it does not offer a real longtime rust protection. However, one has to work with such a subsequent rust protection by painting, or the like, since only structural steel can be used for the thread weld bolt and not precious steel, so as to enable a clean welding with the cross bars which are also made of structural steel. A use of precious steel for the cross bars, which would enable one to also use precious steel for the thread weld bolts and which would remove all corrosion problems, is out of the question because of economical cost saving reasons.